A conventional multi-axis/multi-system NC apparatus is configured as shown in FIG. 30, and has analysis processing units 111 and 112 of plural systems within one NC apparatus. For each system, each analysis processing unit reads each block of an NC program of each system stored in a memory (not shown), and analyzes the program for an interpolation control unit 120 to perform an interpolation process. As a result of the interpolation process by the interpolation control unit 120, a shift pulse of each control axis is generated. An axis control unit 123 outputs the shift pulse to servo control units 102, 103, 202, and 203 and main-axis control units 104 and 204 that drive corresponding axes.
The servo control units 102, 103, 202, and 203 drive coupled servomotors 105, 106, 205, and 206, respectively, following an instructed shift pulse. The main-axis control units 104 and 204 drive coupled main-axis motors 107 and 207, respectively, following an instructed shift pulse. The axis control unit 123 provided in the NC apparatus can drive control axes of the servo control units 102, 103, 202, and 203 or the main-axis control units 104 and 204 that are coupled.
This realizes plural sets of control systems within one unit of hardware. An NC machine tool controlled by a machining program independent in each system and by each control signal and including this NC apparatus can machine each one of or plural products that are the same or different in plural control systems.
In an example of the NC apparatus shown in FIG. 30, the apparatus includes a display device 130, a PLC control unit 121, and an axis exchange control unit 122. The servo control units 102 and 103, the main-axis control unit 104, the servomotors 105 and 106, and the main-axis motor 107 belong to a first system, and the servo control units 202 and 203, the main-axis control unit 204, the servomotors 205 and 206, and the main-axis motor 207 belong to a second system.
In the conventional multi-axis/multi-system NC apparatus, the axis exchange control unit 122 is configured to be able to exchange between the systems a part or a whole of control axes belonging to each system.
In the conventional multi-axis/multi-system NC apparatus, the axis exchange control unit 122 is configured to be able to exchange between the systems a part or a whole of control axes belonging to each system.
FIG. 31 is an example of machine tools that can be controlled by the conventional multi-axis/multi-system NC apparatus. In the example shown in FIG. 31, an X1 axis that drives a tool table #1 and a Z1 axis that shifts a workpiece grasped with a main axis to a longitudinal direction constitute the first system, and an X2 axis that drives a tool table #2 and a Z2 axis constitute the second system.
Normally, in the first system, a program is instructed to the X1 axis, the Z1 axis, and an S1 axis, and machining is performed by combination of the tool table #1 and the main axis S1. In the second system, a program is instructed to the X2 axis, the Z2 axis, and an S2 axis, and machining is performed by combination of the tool table #2 and the main axis S2.
In the conventional multi-axis/multi-system NC apparatus, the axis exchange control unit exchanges the Z1 axis of the first system and the Z2 axis of the second system between the systems for the second system to be able to instruct to the X2 axis, the Z1 axis, and the S1 axis, for example, and machining is performed by combination of the tool table #2 and the main axis S3. With this arrangement, machining time can be shortened, and complex machining can be performed (for example, see Patent Document 1).
The conventional NC apparatus described above needs to control all systems and axes on one unit of hardware. Therefore, the number of controllable systems and the number of controllable axes are naturally limited by memories and a CPU processing speed.
Consequently, when there is a request for increasing the number of systems and the number of axes requiring control, an NC apparatus installed with larger-capacity memories and a higher-speed CPU needs to be additionally developed, and its development cost increases.
Most of such controlling targets requiring a large number of systems and a large number of axes are special exclusive machine tools or large-scale NC machining systems. When development common to an NC apparatus applicable to a general NC machine tool is performed, its manufacturing cost increases, because of hardware that requires performance higher than is necessary to be applied to the general NC machine tool.
To solve a part of the above problems, there has been known a method that one NC apparatus being a master and plural NC apparatuses being slaves are provided, and that each NC apparatus at a slave side performs synchronization control, while each NC apparatus at the slave side is synchronized by a signal and the like from the master NC apparatus.
Because plural slave NC apparatuses operate synchronously with one NC apparatus being a master, the number of simultaneously operable systems can be increased by increasing NC apparatuses being slaves (for example, see Patent Document 2).
There has also been known an automatic machine-control system controlled by plural automatic machines via a communication path, wherein the automatic machine-control system safely and stably controls plural automatic machines by exclusively managing automatic machines having a shared axis indirectly controlled by plural control apparatuses.
This controls occupancy of a shared axis that can be indirectly controlled from other automatic machine via a communication path, and performs exclusive control to avoid simultaneous indirect control from plural control apparatuses. The above automatic machine-control system is such that, in an automatic machine-control system in which a master automatic machine and slave automatic machines of which occupancy right is obtained by the master automatic machine perform co-operation, when two or more master automatic machines are present to control the slave automatic machines, the slave automatic machines receive plural instructions from different automatic machines, and operation is not guaranteed. Therefore, the automatic machine-control system described above controls the occupancy right of an automatic machine controlled by other control apparatus, thereby performing safe and stable control (for example, see Patent Document 3).    Patent Document 1: Japanese Patent Application Laid-open No. H3-28908    Patent Document 2: Japanese Patent Application Laid-open No. H9-146623    Patent Document 3: Japanese Patent Application Laid-open No. 2005-173849